Many medicinally active ingredients have unpleasant tastes, e.g. bitter or pungent tastes, and/or unpleasant odors. Because such medicinal substances cannot be easily taken orally by young children and the aged, the dosage and administration recommendations are sometimes neglected so that the so-called compliance problem occurs at times.
Therefore, to provide pharmaceutical preparations with improved tastes and odors, several approaches have heretofore been suggested. Among them are (1) the method comprising adding a corrigent such as a sweetener to a medicinally active ingredient and processing the mixture into a preparation, (2) the method in which the medicinally active ingredient is absorbed physically on a carrier, (3) the masking method comprising microencapsulating or cladding the medicinally active ingredient with a wall-forming or coating material, and (4) the method comprising complexing the medicinally active ingredient with an ion exchange resin.
The first-mentioned method (1), however, has the disadvantage that depending on the threshold bitterness of the medicinally active ingredient, inter-patient differences in gustatory sensibility, etc., the bitterness, for instance, cannot be sufficiently controlled. The second-mentioned method (2) calls for the use of an absorbent in a large quantity for effective absorption of the medicinally active ingredient, leading to an increase in dosage unit size. The third-mentioned method (3) is also disadvantageous in that an excessive increase in wall or film thickness detracts from the gastrointestinal absorption of the medicinally active ingredient while an excessive reduction in wall or film thickness results in a premature development of bitterness, with the result that its bitterness can hardly be controlled efficiently without decreasing the absorbability of the active ingredient. Moreover, the pharmaceutical manufacturing process is complicated of necessity and, yet, no commensurate suppression of the unpleasant taste and/or odors can be expected.
Regarding the fourth-mentioned method (4), British Patent 1462356, Research Disclosure 176019 (Derwent WPI Acc No. 78-92367A/51) and Research Disclosure 176020 (Derwent WPI Acc No. 78-92368A/51) describe complexes of .beta.-lactam antibiotics with cation exchange resins and complexes of penicillin drugs with anion exchange resins. By this technology employing an ion exchange resin, the bitterness of medicinally active ingredients can be fairly well controlled.
However, it takes a large quantity of an ion exchange resin, relative to a drug, to prepare such a complex of the drug with the ion exchange resin so that the preparation is increased in size and the drug is diluted. Moreover, in a study using beagle dogs, the inventors of this invention found that the complexing of a drug with an ion exchange resin resulted in a reduction in the rate of drug dissolution so that the gastrointestinal absorbability of the drug is lowered.